The conventional method in computer technology is to install an operating system (OS) in a computer so that when the computer is booted, the OS, the device drivers, and applications in a hard disk of the computer will be loaded and executed after the basic booting process.
As the computer becomes more powerful, more and more applications are developed, and different functions of computers are also developed to meet the demands. For example, a typical application is to use a computer in conjunction with a multimedia player or a household appliance to become a more versatile multimedia system.
Because there are pros and cons for different OS, industrial suppliers provide multimedia systems with dual OS. The conventional technique is to configure the hard disk into to two hard-disk areas. The first area installs a first OS for normal computer operation mode, and the second area installs a second OS for multimedia operation mode.
However, when the computer completes the booting process, all the connected peripherals are activated and in a ready-to-play state, which consumes a considerable amount of power. To save the power consumption and prolong the life span of the computer system, most operating systems of personal computers, such as Windows XP, Windows 2000, and Windows Me, integrate power management function of the advanced configuration and power interface (ACPI). Therefore, the power management operation can be performed through the ACPI interface.
The ACPI interface manages the power usage of the peripherals. The ACPI interface specifies various power management states, including active, hibernation, standby and shutdown. Based on the user's setting, the computer system can enter the standby or hibernation state. The standby mode is a low-power state, and the hibernation state reduces further power consumption. In a typical ACPI structure, the power states are defined as:
S0: normal power supply state;
S1: first stage standby mode, in which the power to a central processing unit (CPU), memory and fan stays on while the power to monitor and hard disk is shut off;
S2: second stage standby mode, in which the power to CPU, cache, monitor and hard disk are off;
S3: third stage standby mode, in which only minimum power stays supplied to RAM;
S4: hibernation state, in which power to all the devices and elements are off, with the operating system storing all the data and execution states before terminating the power supply to the devices and elements; and
S5: shutdown state, in which all the power supply is turned off.
Based on the user's setting, the computer system can enter the standby or hibernation state. The standby mode is a low-power state, and the hibernation state reduces further power consumption.